The invention relates to a control circuit for underground mining equipment such as a getting machine or conveyor system equipped with apparatus which is operatively dependent on the operating voltage and/or phase of electric current in a supply cable wherein such equipment is connected by a monitoring conductor to a power contactor situated in the mine gallery and to a monitoring relay.
West German patent publication No. 23 50 963 discloses means for switching ON and OFF the driving motor of getting machines, more particularly of drum cutter loaders, which are provided with a motor contactor that can be controlled by a relay and with a bridgeable ON-key switch and an OFF-key switch, both of which are connected in series with a relay.
The apparatus of getting machines and in conveyor systems include means which depend on the operating voltage and/or phase of a current supply. Such means include, for example, thyristor controlled systems which must be set into their electrically inoperative position, and more specifically, the thyristors must be extinguished when the OFF-key switch is actuated before the roadway contactor is switched OFF.